The invention pertains to a multi-stage screw compressor system. Preferably, the screw compressor system is a “dry-running” system for high pressures, typically 40 bar and above. A preferred area of applicability is the production of compressed air for blow-molding of plastic bottles.
A two-stage screw compressor system is known from U.S. Pat. No. 3,407,996 (corresponding to DE-A-1628201). It has a gearbox with a perpendicular mounting wall, attached to which are two adjacent compressor stages that cantilever parallel with one another. Each compressor stage comprises a screw compressor with two mutually engaging screw rotors. Located in the gearbox is a transmission with a drive gear that meshes with two driven gears that rotate the rotors of the two screw compressors. Also disclosed in the document is that the invention described in it can also be used in multistage compressor systems with more than two stages. However, there is no indication of how further compressor stages can be arranged, and the design that is described in detail has no place for further compressor stages.
A similar two-stage screw compressor system is also known from DE 299 22 878.9 U1.
The object of the invention is to design a three-stage screw compressor system that can deliver a compressed gaseous fluid, in particular compressed air, at a very high pressure, typically about 40 bar and above, and that is characterized by its space-saving design, its simplicity and robustness. In another embodiment of the invention, the three-stage screw compressor system according to the invention allows the ratio of the RPM's of the three compressor stages to be changed in a simple manner.
To meet this objective, a three stage screw compressor is provided with the features according to claim 1 according to the invention. The dependent claims refer to further advantageous features of the invention.
The screw compressor system according to the invention can compress gaseous fluid, in particular air, to a very high pressure ratio, for example 40:1, using only three compressor stages; thus, compressed air can be supplied at a high pressure as is required for industrial manufacturing processes such as blow-molding of plastic bottles.
In the screw compressor system according to the invention, the screw compressors that constitute the first and second stages are located above the horizontal plane that runs through the rotating axis of the drive gear, whereas the screw compressor of the third stage is located below the screw compressors of the first and second stages and below the horizontal plane running through the rotating axis of the drive gear, and whereas its driven gear meshes with the drive gear near its lowest point. This results in an especially advantageous utilization of the existing space configurations and thus a space-saving, compact design of the compressor system. By using different exchangeable bearings and flange parts, the position of the drive shaft can be changed in the horizontal direction and the position of the third compressor stage can be changed in the vertical direction in order to adjust the gearing configuration to different diameters of gears and thus to different RPM ratios of the compressor stages.